SOOT OXIDATION IN A SILENT DISCHARGE

A study of soot oxidation in silent discharge aiming for the development of an efficient soot removal technique, is presented. The soot collected on the filter decreased in silent discharge by the addition of H2O and/or O2 to Ar carrier gas. In the case of a flow system also, the soot concentration was reduced with an increase of residence time in the discharge reactor. These facts support the conclusion that the soot particles were oxidized by OH radicals generated by the destruction of water vapor in the exhaust gas. To explain the soot reduction by OH radicals quantitatively, simple kinetic simulations were carried out. In this model, the electron energy in the discharge was adjusted to obtain agreement with experimental measurements of OH radical concentration as measured by resonance absorption spectroscopy. The calculated results well explained the observed trends of soot reduction when the collision efficiency of OH radicals with the soot surface was assumed to be 0.1.